Florian Thauvin's brace for Bastia inflicted a first Ligue 1 defeat in over six months on Francis Gillot's Bordeaux.
The 19-year-old stunned Les Girondins with two quickfire goals in the opening 17 minutes, Yoan Gouffran just managing to respond just before the break.
But when Wahbi Khazri doubled the Corsicans' lead once again with a well-taken free-kick, Bordeaux had no answer and duly lost their first Championnat outing since April.
It took just six minutes for Bastia to take the lead, as Fethi Harek's delivery was clumsily spilled on to Thauvin's feet by Ludovic Obraniak.
The teenage midfielder steeled himself before calmly slotting the ball past Cedric Carrasso.
The Corsicans doubled their lead in the 17th minute, Carrasso pushing Tofilou Maoulida's drive away, but that man Thauvin was lurking and poked the ball home.
Bordeaux halved the deficit on the half-hour mark as Yoan Gouffran volleyed Obraniak's corner beyond Macedo Novaes.
But Poland international Obraniak had his head in his hands three minutes before the break as his wicked shot shaved paint off the wrong side of a post.
Bordeaux had a better chance to equalise as play resumed, David Bellion repelled in spectacular fashion by Novaes when one-on-one with the Bastia keeper.
Carrasso also had his work cut out as Wahbi Khazri arrived in space to rifle in a fizzing shot.
Khazri would not be denied in the 55th minute, though, the young Corsican drilling home a stunning free-kick from 25 yards after Thauvin had been felled by Henrique.
Obraniak repeated his first-half trick with another effort that glanced the woodwork before Bordeaux had one last opportunity to close the gap.
Jeremy Choplin blundered in possession, leaving Bellion free in front of Novaes once more, but the Girondins striker blinked first and Bastia's points were safe.